The present disclosure relates to a solar panel.
Japanese Laid-Open Patent Publication No. 2017-34004 discloses a conventional solar panel that includes a protective cover, a back cover, solar cells, conductors, a sealing member, and output leads.
The protective cover is made of glass and has light transparency allowing light to pass through from a first front surface of the protective cover to a first back surface of the protective cover. The back cover is made of plastic and includes a second front surface, which is joined to the sealing member, and a second back surface, which is located on the opposite side to the second front surface. The back cover includes through-holes that extend from the second front surface of the back cover to the second back surface of the back cover. The through-holes allow the output leads to be inserted. The solar cells are arranged in a grid pattern in a first direction and a second direction, which intersects the first direction. The conductors are formed into a tabular shape and extend in the second direction. The conductors are each located on the outer side of one of the two solar cells at the opposite ends of the array of the solar cells arranged in the first direction. The solar cell and the conductor that are located adjacent to each other in the first direction are connected to each other to permit electricity to flow therebetween.
The sealing member retains all the solar cells and all the conductors in a sealed state between the protective cover and the back cover. The sealing member also includes through-holes that allow the output leads to be inserted. Each output lead includes a distal end portion and an extending portion. The distal end portion is arranged along the second front surface of the back cover and is connected to the corresponding conductor at a position different from where the solar cell is connected. The extending portion connected to the distal end passes through the through-holes of the sealing member and the back cover, extends to the second back surface of the back cover, and is connected to a terminal box.
The solar panel allows the electric power generated by the solar cells to be transmitted to the terminal box through the output leads connected to the solar cells.
In the above-described conventional solar panel, even if the back cover expands in the second direction due to thermal expansion during manufacturing or use, the conductors resist being expanded in the second direction and are unlikely to conform to the back cover since the conductors are formed into a tabular shape. Thus, the solar cells and the conductors are displaced relative to each other in the second direction, and the connections among the solar cells, the conductors, and the output leads that permit electricity to flow are likely to break.
Furthermore, in the solar panel, when the back cover thermally expands, the output leads follow the back cover and move in the first direction away from the solar cells. Thus, stress acts on the connection parts between the distal ends of the output leads and the conductors in a direction of peeling the distal ends of the output leads off the conductors. Thus, in the solar panel, the distal ends of the output leads are easily peeled off the conductors. For these reasons, the solar panel is likely to cause electrical continuity failure due to thermal expansion. In particular, in recent years, the protective cover may be made of plastic from the viewpoint of reducing the weight. However, since such a protective cover has a thermal expansion coefficient greater than that of the glass protective cover, the above-described problem becomes more noticeable in the solar panel with the protective cover and the back cover both made of plastic.